This invention is in the fields of immunology and cancer diagnosis and therapy. More particularly it concerns antibodies specifically binding growth factor receptors, hybridomas that produce these antibodies, immunochemicals made from the antibodies, and diagnostic methods that use the antibodies. The invention also relates to the use of the antibodies alone or in combination with cytotoxic factor(s) in therapeutic methods. Also encompassed by the invention is an assay for tyrosine kinases that are involved in tumorigenesis.
Macrophages are one of the effector cell types that play an important role in immunosurveillance against neoplastic growth in vivo. In vitro, cell-mediated cytotoxicity requires selective binding between activated macrophages and target cells as well as the concomitant release of cytotoxic factors. Some of the cytotoxic factors secreted by activated macrophages include reactive oxygen species such as the superoxide anion and hydrogen peroxide, arginase, interleukin 1, and tumor necrosis factor-xcex1 (TNF-xcex1). Acquired resistance to the toxic effects of these factors by tumor cells could be one mechanism which leads to the onset and spread of tumor formation in vivo.
The observation that TNF-xcex1 can act as a potent effector of the macrophage-mediated antitumor response provides a rationale for its use in further studies on the regulation of tumorigenesis in vivo and tumor cell growth in vitro. The genes encoding TNF-xcex1 and TNF-xcex2, a structurally related cytotoxic protein formerly known as lymphotoxin, have been cloned and the corresponding proteins expressed in Escherichia coli. These proteins display an array of biological activities, including induction of hemorrhagic necrosis of Meth A sarcomas in vivo, inhibition of the growth of certain tumor cells in vitro, synergistic enhancement of the in vitro anticellular effects of IFN-xcex3, activation of human polymorphonuclear neutrophil functions, and inhibition of lipid biosynthesis. Recently, rHuTNF-xcex1 was shown to augment the growth of normal diploid fibroblasts in vitro. The divergent proliferative responses in the presence of rHuTNF-xcex1 are sometimes related to variations in TNF binding.
Growth factors and their receptors are involved in the regulation of cell proliferation and they also appear to play a key role in oncogenesis. Of the known proto-oncogenes, three are related to a growth factor or a growth factor receptor. These genes include c-sis, which is homologous to the transforming gene of the simian sarcoma virus and is the B chain of platelet-derived growth factor (PDGF); c-fms, which is homologous to the transforming gene of the feline sarcoma virus and is closely related to the macrophage colony-stimulating factor receptor (CSF-IR); and c-erbB, which encodes the EGF receptor (EGFR) and is homologous to the transforming gene of the avian erythroblastosis virus (v-erbB). The two receptor-related proto-oncogenes, c-fms and c-erbB, are members of the tyrosine-specific protein kinase family to which many proto-oncogenes belong.
Recently, a novel transforming gene was identified as a result of transfection studies with DNA from chemically induced rat neuroblastomas. This gene, called neu, was shown to be related to, but distinct from, the c-erbB proto-oncogene. By means of v-erbB and human EGFR as probes to screen human genomic and complementary DNA (cDNA) libraries, two other groups independently isolated human erbB-related genes that they called HER2 and c-erbB-2 respectively. Subsequent sequence analysis and chromosomal mapping studies revealed that c-erbB-2, and HER2 are species variants of neu. A fourth group, also using v-erbB as a probe, identified the same gene in a mammary carcinoma cell line, MAC 117, where it was found to be amplified five- to ten-fold.
This gene, which will be referred to herein as HER2, encodes a new member of the tyrosine kinase family; and is closely related to, but distinct from, the EGFR gene as reported by Coussens et al., Science 230, 1132 (1985). HER2 differs from EGFR in that it is found on band q21 of chromosome 17, as compared to band p11-p13 of chromosome 7, where the EGFR gene is located. Also, the HER2 gene generates a messenger RNA (mRNA) of 4.8 kb, which differs from the 5.8- and 10-kb transcripts for the EGFR gene. Finally, the protein encoded by the HER2 gene is 185,000 daltons, as compared to the 170,000-dalton protein encoded by the EGFR gene. Conversely, on the basis of sequence data, HER2 is more closely related to the EGFR gene than to other members of the tyrosine kinase family. Like the EGFR protein, the HER2 protein (p185) has an extracellular domain, a transmembrane domain that includes two cysteine-rich repeat clusters, and an intracellular kinase domain, indicating that it is likely to be a cellular receptor for an as yet unidentified ligand. HER2 p185 is referred to as p185 or the HER2 receptor herein.
Southern analysis of primary human tumors and established tumor-derived cell lines revealed amplification and in some cases rearrangement of the EGF receptor gene. Amplification was particularly apparent in squamous carcinomas and glioblastomas. The HER2 gene was also found to be amplified in a human salivary gland adenocarcinoma, a renal adenocarcinoma; a mammary gland carcinoma, and a gastric cancer cell line. Recently, Slamon et al., Science 235, 177 (1987) demonstrated that about 30% of primary human breast carcinoma tumors contained an amplified HER2 gene. Although a few sequence rearrangements were detected, in most tumors there were no obvious differences between amplified and normal HER2 genes. Furthermore, amplification of the HER2 gene correlated significantly with the negative prognosis of the disease and the probability of relapse.
To investigate the significance of the correlation between overexpression and cellular transformation as it has been observed for proto-oncogenes c-mos and N-myc, a HER2 expression vector and a selection scheme that permitted sequence amplification after transfection of mouse NIH 3T3 cells was employed by Hudziak et al., Proc. Natl. Acad. Sci. (USA) 84, 7159 (1987). Amplification of the unaltered HER2 gene in NIH 3T3 cells lead to overexpression of p185 as well as cellular transformation and tumor formation in athymic mice.
The effects of antibodies specifically binding growth factors or growth factor receptors has been studied. Examples are discussed below. Rosenthal et al., Cell 46, 301 (1986) introduced a human TGF-xcex1 cDNA expression vector into established non-transformed rat fibroblast cells. Synthesis and secretion of TGF-xcex1 by these cells resulted in loss of anchorage-dependent growth and induced tumor formation in nude mice. Anti-human TGF-xcex1 monoclonal antibodies prevented the rat cells from forming colonies in soft agar, i.e. loss of anchorage dependence. Gill et al. in J. Biol. Chem. 259, 7755 (1984) disclose monoclonal antibodies specific for EGF receptor which were inhibitors of EGF binding and antagonists of EGF-stimulated tyrosine protein kinase activity.
Drebin et al. in Cell 41, 695 (1985) demonstrated that exposure of a neu-oncogene-transformed NIH 3T3 cell to monoclonal antibodies reactive with the neu gene product, cause the neu-transformed NIH 3T3 cell to revert to a non-transformed phenotype as determined by anchorage independent growth. Drebin et al. in Proc. Natl. Acad. Sci. 83, 9129 (1986) demonstrated that in vivo treatment with a monoclonal antibody (IgG2a isotype) specifically binding the protein encoded by the neu oncogene significantly inhibited the tumorigenic growth of neu-transformed NIH 3T3 cells implanted into nude mice.
Akiyama et al. in Science 232, 1644 (1986) raised antibodies against a synthetic peptide corresponding to 14 amino acid residues at the carboxy-terminus of the protein deduced from the c-erbB-2 (HER2) nucleotide sequence.
Growth factors have been reported to interact in both a synergistic and an antagonistic manner. For example, TGF-xcex1 and TGF-xcex2 synergistically enhance the growth of NRK-49F fibroblasts, whereas PDGF down regulates EGF receptor function on 3T3 cells. A variety of transformed cells secrete factors which are believed to stimulate growth by an autocrine mechanism. Sugarman et al., Cancer Res. 47, 780 (1987) demonstrated that under certain conditions, growth factors can block the antiproliferative effects of TNF-xcex1 on sensitive tumor cells. Specifically, epidermal growth factor (EGF) and recombinant human transforming growth factor-xcex1 (rHuTGF-xcex1) were shown to interfere with the in vitro antiproliferative effects of recombinant human tumor necrosis factor-xcex1 (rHuTNF-xcex1) and -xcex2 on a human cervical carcinoma cell line, ME-180. The inhibitory effect could be observed at EGF or rHuTGF-xcex1 concentrations of 0.1 to 100 ng/ml, and was maximal between 1 and 10 ng/ml. This response was apparently not due to down regulation of the TNF receptor or to alteration of the affinity of TNF-xcex1 for its receptor. Since the antiproliferative effect of recombinant human interferon-xcex3 was not significantly affected by the presence of EGF or rHuTGF-xcex1, the inhibition was specific for recombinant TNFs and was not due solely to enhanced proliferation induced by the growth factors. Neither growth factor had a substantial protective effect on the synergistic cytotoxicity observed when tumor cells were exposed simultaneously to rHuTNF-xcex1 and recombinant human interferon-xcex3. TGF-xcex2 can also interfere with the antiproliferative effects of rHuTNF-xcex1 in vitro. At concentrations of less than 1 ng/ml, TGF-xcex2 significantly antagonized the cytotoxic effects of rHuTNF-xcex1 on NIH 3T3 fibroblasts. Since EGF, platelet-derived growth factor, and TGF-xcex2 all enhanced NIH 3T3 cell proliferation, but only TGF-xcex2 interfered with rHuTNF-xcex1 cytotoxicity, the protective effects of TGF-xcex2 were not related in a simple manner to enhanced cell proliferation. rHuTGF-xcex1 and TGF-xcex2 did not have a significant protective effect against rHuTNF-xcex1-mediated cytotoxicity on two other tumor cell lines, BT-20 and L-929 cells.
It is an object of the subject invention to provide antibodies capable of inhibiting growth factor receptor function.
It is a further object of the invention to provide an improved assay for the HER2 receptor.
It is a further object of the invention to provide improved methods of tumor therapy.
It is a further object of the invention to provide a method of inhibiting the growth of tumor cells which overexpress a growth factor receptor and/or growth factor.
It is a further object of the invention to provide a method for treating a tumor by treatment of the tumor cells with antibodies capable of inhibiting growth factor receptor function, and with cytotoxic factors such as tumor necrosis factor.
A still further object of the invention is to provide an assay for tyrosine kinases that may have a role in tumorigenesis.
Other objects, features and characterisitics of the present invention will become apparent upon consideration of the following description and the appended claims.
The subject invention relates to monoclonal antibodies specifically binding the external domain of the HER2 receptor. The invention also relates to an assay for the HER2 receptor comprising exposing cells to antibodies specifically binding the extracellular domain of the HER2 receptor, and determining the extent of binding of said antibodies to said cells. Another embodiment of the invention relates to a method of inhibiting growth of tumor cells by administering to a patient a therapeutically effective amount of antibodies capable of inhibiting the HER2 receptor function. A further embodiment of the invention relates to administering a therapeutically effective amount of antibodies capable of inhibiting growth factor receptor function, and a therapeutically effective amount of a cytotoxic factor. A still further embodiment of the invention is an assay for tyrosine kinases that may have a role in tumorigenesis comprising exposing cells suspected to be TNF-xcex1 resistant to TNF-xcex1, isolating those cell which are TNF-xcex1 resistant, screening the isolated cells for increased tyrosine kinase activity, and isolating receptors and other proteins having increased tyrosine kinase activity.